Variable and Fixed Loops Discovery

That is interesting!

Wonder if it matters what brand of switches.  Many of my Christmas layouts were designed to have 2 switches connected that were on different "loops".  Thru dumb luck, and nothing else, I started using the external power post on my switches when I got my MRC Dual 270.  Lucky break!

- walt

Well it makes sense but it did not dawn on me until the problem surfaced.  Since the switches were powered by the track power it is logical that power could then go to an unpowered track connected to that switch.   I have since removed the switches entirely and have two totally separate loops.  Both on DCS, but one on variable 1 and one is on fixed 1.    So the inside loop can run my Thomas engines, after all the Christmas layouts are for the kids, right?   

I know you've removed the switches and things are working great for Christmas, Good stuff. I'm still curious though  if you had an insulated center rail joint at one end of insulating track section. What is an insulating track section anyway ? insulated  outside rail for accessories ??

If it's  center rail had one insulting pin or open joint, there's no way power can flow from one loop to the other,Only the common should be hooked up to the AIU when dealing with switches. What am I missing??

Gregg,  I was using a Realtrax 5" insulated section.  There are 3 short wires on the underside that connect the 3 rails and the rails themselves are cut in the middle.  At first I just had the center rail disconnected but then I disconnected all 3 rails by removing the 3 short wires pieces on the bottom of the insulated track section.  The two switches(curved side) were on either side of the insulated section to connect the two loops.  The switches were track powered and wired together to throw as one switch from one AIU connection.  Since the switch on the outer loop had DCS 18v power it went to the inner loop to power the other switch and hence the track.  That is what I understand.  Once I disconnected the 3 wires to one switch I had no more problem with power to the inner loop when I did not want it.  I hope I explained that properly.   

Only two wires are needed to throw the switches through or out, and ground/common is used to trigger the switch.  The bleed over of track power is probably related to your third wire and/or the two tracks being wired out of phase in relation to each other(hot/common switched on one).

Dave,

This is probably one reason MTH recommends using accessory power for switches when using DCS.

Joe,

This is probably one reason MTH recommends using accessory power for switches when using DCS.

That's most likely true, however, it's probably not the most important reason.

Running switch tracks using track power does not typically cause any voltage anomalies at all. His issue is because he's using the same track power to throw 2 switch tracks on two separate loops. That's what causes the connection between the two loops.

A more important reason is to avoid sending the DCS signal through the switch motor or switch coil windings. That has the potential to degrade the DCS signal.

 His issue is because he's using the same track power to throw 2 switch tracks on two separate loops. That's what causes the connection between the two loops.

Not that it matters now.,

To throw 2 switches at the same time can't each switch have it's own track  power supply and the commons control the throw.

Anyway thanks the posts... I think it finally sunk in. takes a while though.

Dave,  you stated both switches set to throw as one, yet you say when you throw "1" switch to curve it was ok.  I don't think the issue is the switches, or your method of using the insulating track.

it maybe how you wired the switches to the Aiu.  As Rob mention you have center rail and common ground passing thru the switch control mechanism.  It does bring up the interesting question of how an engine would respond moving from a dcs block into a conventional block.

you could set the switches as manual only, no controller connections and see how it behaves when throwing switches manually.  

I think you would find no issues, but when a train moves thru the block you may get some issues as the engine connects the blocks.  G

Gregg,

To throw 2 switches at the same time can't each switch have it's own track  power supply and the commons control the throw?

Absolutely. However, GGG has the real reason why there's a problem.

it maybe how you wired the switches to the AIU.

Somehow, he managed to connect the Hot wires of both loops together, rather than just the Common wires.

GGG,  When I said moving the switch to curve the inner loop started up, I meant manually moving that switch by rotating the switch lantern and not through the AIU.  I wasn't clear on that.  

Loops are correctly wired, red to red and black to black.  Also switches wired to AIU in accordance with AIU manual.   Are you saying that track power cannot go through the 3 hookups(straight, curve, gnd)  on the swicthes to power the other loop?  After removing all 3 short wires on the insulated section I still had power go from one loop to the other but after removing the 3 wires to one of the switches I then had no power transfer to the inner loop.  

Yes, it is definitely better to use aux power for the switches for the reasons Barry gave, but since I am on a carpet central and not a permanent layout I just use track power to minimize wiring.  I have not had DCS signal issues but my layouts are generally no larger than 6x10 or so.  

cngw:  It seems a conventional engine would take off full bore going from a 'conventional' track to a DCS track due to the much higher voltage.  IF your DCS engine running on 18v goes to a conventional loop running on less than 12-14v it would do something else, either slow down, or stay the same if there is still DCS signal on that loop.  You can run DCS down to 8-10v I believe.  

Thanks for all the input and good ideas.   

Dave,  I have not worked with an AIU or MTH Switches, but...  Normally when the switch is powered from the track you have center rail power available to the coils that move the switch.  Track ground has to be applied to the appropriate coil to energize it and allow the switch frog to move.  The manual switch does this.  If you have both switches on the same AIU terminal, then the center rail power can move thru one coil and in series thru the other coil and energize the center rail of the other block.  Whether this is from the switching mechanism or the non de-railing function I can't be sure without looking inside the switch.

I would try using the manual lever controllers provided to switch each switch manually and see how that work, or put each switch on a separate AIU channel.  G

GGG,

   What you are saying is good for Lionel 072 type switches, the MTH switches

might work in a slightly different manner, can't remember the difference however,

quit using the MTH stuff a long time ago, and went with FasTrack and old 072 switches.

PCRR/Dave